Fundamentals of Computer Animation Wrap-up Overview

Animation Timeline in Movies Conventional Animation (Techniques/Process) Role of the Computer 3D Animation Reading: Jessica K. Hodgins and James F. O'Brien “Computer Animation” (check web site)

Timeline  The Illusion of Motion 1824, Peter Mark Roget,"Persistence of Vision with Regard to Moving Objects“ a series of images shown in rapid sequence can appear to move fluidly (i.e. a flip book or film projector)

Timeline  Movies (1895) age of movie camera and projector begins experimentors discover they can stop the crank and restart it again to obtain special effects (1914) Gertie, Windsor McCay (newspaper cartoonist) first popular animation (1928) Steamboat Willie, Disney an early cartoon w/ sound cartoons seem plausible as entertainment (1933) King Kong, Willis O’Brien (1930’s & 40’s) Golden age of cartoons Betty Boop, Popeye, Porky Pig, Daffy Duck, Bugs Bunny, Woody Woodpecker, Mighty Mouse, Tom & Jerry (1937) Snow White, Disney animated feature film cost is $1.5M

Timeline  Movies (cont) (1982) Tron, MAGI movie with a computer graphics premise (1984) Last Starfighter computer graphics was used interchangably with actual models of the spaceship (1993) Jurassic Park computer graphics is used to create living creatures that are meant to appear realistic (1995) Toy Story, Pixar full-length feature film done entirely with 3D computer animation (2000) CyberWorld 3D, IMAX 3D IMAX full-length feature film including characters from popular 3D movies such as ANTZ and The Simpsons’ Homer

Conventional Animation Techniques Drawing on film Multiple drawings Rotoscoping (project film of real actors onto drawing paper) Stop motion animation Acetate cels, multiple plane cells

Conventional Animation Process Storyboard Key frames drawn Straight ahead vs. pose-to-pose Intermediate frames filled in (inbetweening) Trial film is made (called a pencil test) Pencil test frames transferred to cels

Conventional Animation Process

Role of the Computer In-betweening Disney’s CAPS system artistic example: Hunger, Peter Foldes 1974 Disney’s CAPS system scanned artist drawings are read in "cels" are colored online (broad color palette, exact color matching) compositing is done online (background, 2D drawings, 3D animation) 3D effects can be created with 2D drawings (e.g. Beauty and the Beast) used in every film since Beauty & Beast 3D graphical worlds can experiment more easily with actor position, camera position can perform more complex camera moves exchange labor to create drawings with labor to build and animate 3D world

3D Animation 3D animation is similar to stop motion animation King Kong (1932) http://www.stopmotionanimation.com/ Flash Gordon (1972)

3D Animation Stop motion animation (Nightmare Before Christmas) 3D keyframing (Luxo Jr.) Performance animation and motion capture (Donkey Kong Country) Which must be done straight-ahead and which can be animated pose-topose?

Keyframing Key frames mark important visual transitions (extremes of action) Inbetweening is creation of intermediate frames between the key frames Can easily be calculated by computer

Temporal Sampling Film recording takes samples of an image at fixed time intervals 24 frames per second for film 30 frames per second for video human eye "sees" continuous motion Sometimes, fewer keyframes are required to describe the motion, especially for “pencil tests” or rough choreography (e.g., Lost World)

Smooth Motion  (1) Passive Physics No internal energy source and move only when an external force acts on them. Read for use when: physical laws encoded initial conditions specified Pools of water, clothing, hair, leaves

Smooth Motion  (3) Passive Physics Clothing (Geri’s Game) Water (Antz) “Rigid” body physics (crashing space pods in Phantom Menace) Geri’s Game, Pixar Animation Studios

Smooth Motion  (2) Active Physics User specifies keyframes (start, end, middle) User specifies constraints (e.g. laws of physics) System searches for minimum energy motion to accomplish goals A. Witkin and M. Kass, “Spacetime Constraints”, SIGGRAPH ‘88.

Smooth Motion  (3) Active Physics and Simulation Control an animated character as we would control a robot behavior is simulated a "control system" sends proper signals to the character’s "muscles" over time Mark Raibert’s leg lab at MIT http://www.ai.mit.edu/projects/leglab/

Noise Motion We generally don’t want motion to be too smooth The eye picks up symmetries and smooth curves and interprets them as artificial or fake By adding noise, we can add texture to smooth motion K. Perlin, “An Image Synthesizer”, Computer Graphics, 19(3), July 1985. Perlin, Improv system (K. Perlin and A. Goldberg, SIGGRAPH ‘96). Applets: http://www.mrl.nyu.edu/~perlin/

Noise Motion Motion capture (natural noise!)